Two families of plugins
Those that translate the page as it is displayed. Your content stays in its original language; the plugin lays the translation over it. When you deactivate it, the site simply goes back to its original language. Nothing is lost from your content.
Those that keep each language as separate pages. Your “Our rooms” page exists in several copies, one per language. When you deactivate the plugin, these copies become ordinary pages on your site. You then need to remove them, so you don't end up with duplicate pages.
In what order
- Install the new plugin without deactivating the old one. Let it read your site and show you the result.
- Check a translated page before paying for anything.
- Deactivate the old plugin once the new one is in place. Two translation plugins active at the same time serve the same pages twice and slow the site down.
- Keep the old one deactivated for a few weeks rather than deleting it: its settings remain, and you can go back.